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Appeared on: Monday, February 18, 2002
Mt. Rainier Format


1. Page 1

CD-MRW Format

Source: Philips

- Introduction:
The Mount Rainier Technical Group is an industry organization that has defined a defect managed format for standard CD-RW media. The format is named CD-MRW (Mount Rainier RW).

Mount Rainier enables native OS support of data storage on CD-RW. This makes the technology far easier to use and allows the replacement of the floppy. This is done by having defect management in the drive, by making the drive 2k addressable, by using background formatting, and by standardizing both command set and physical layout. The new standard is promoted by Compaq, Microsoft, Philips, and Sony and is supported by 38 industry leaders: OS vendors, PC-OEM's, ISV's, chip makers, and media makers.

- How this will come in the market?

With new recorders under the "CD-MRW" code name. These new CD-MRW ("M" is short for "Mt. Rainier") disc drives include defect management, and address the disk interchange problem by specifying the UDF format for use on CD-RW disks to ensure a standard for disk interchange between different computer systems. To take advantage of these new features, the drive requires a new type of software to support CD-RW media.

- In which RW format can be used?

Mt. Rainier can be used in both 1-4x and 4-10x (HS-RW) formats. The file system of the Mt. Rainier format would be, UDF 1.02 or 2.01.

- What's new?

The Mount Rainier project has 5 key elements:

- Physical defect management by the drive
- Logical write-addressing at 2k
- Background formatting
- Command set implementation
- Compatibility and standards-compliance

Defect Management in the Drive

In the last few years, several solutions have been developed to allow easy drag & drop writing upon both CD-R and CD-RW media. Most solutions are based upon UDF v1.50, which includes defect management. However this is done by the software not the drive. A drive which includes defect management will handle them easier and quicker. Also that makes the file-system and the compatible applications since they don't have to knowledge of the drive/media defect characterization & capabilities. CD-ROMs have no knowledge on how handling defect-sparing. The Mount Rainier group ensures that CD-ROM's will be able to read Mount-Rainier disks though a generic read-driver, allowing read-back compatibility. This drive will be intergraded inside Windows OS (hence the Microsoft participation)...

2 K Addressing

With the current CD-RW format, a block-size of 64 kB is required when most data systems are based on 2k or 4k addressing capabilities. The Mount-Rainier group has solved this issue and adopted 2k logical addressing. This allows file-system and caching capabilities of the host to be transparent for the media related block-size.

Background Formatting

We all know that in order to use a packet writing software, the necessary formatting must be done. The Mt. Rainier format solves that <problem> also. After the disc is inserted to a CD-MRW drive, a background formatting will be done, invisible to end user. That minimizes the time which a user has to wait until the disc is ready for sure. The formatting is very quick (few seconds). The use-experience is optimized by ensuring that drag & drop data-storage tasks will get priority above progress of "de-icing" and "finalization" in the background by the drive.

Command Set

The Mt. Rainer group will add all commands and mode-pages in the MMC-3 standard.

Compatibility and Standardization

The Mount Rainier group main focus is to make sure that there will be no compatibility issues with existing and future drive. Also the need for vendor-related legacy support will be reduced.


2. Page 2

CD-MRW Format - Page 2

Source: Philips

- Techical information

From the perspective of the CD-RW System Description, the entire capacity of a MRW disc consists of a single session containing a single track of 32 sector fixed packets.


Track/Session Structure of a CD-MRW Disc

The MRW disc does have this format, but the CD-MRW Defect Management & Physical Formatting requires additional features, built upon the basic format:

Lead-in, Part A: TOC, no change

Lead-in, Part B: TOC (in sub-channel Q) along with MTA (information is stored in main channel). Prior to CD-MRW, the lead-in has always been recorded track-at-once. With this new format, it is recorded as fixed packets. The MTA use begins with the packet that precedes the pre-gap. When needed, the MTA grows backward toward the disc center.

Program Area, Part A: Track 1 pre-gap has a fixed size of 150 sectors. The TDB identifies the track as a fixed packet track with packet size = 32.

Program Area, Part B: The General Application Area (GAA) is a segment of the track that is NOT covered by the defect management system. This is fixed at 32 packets (2 MB of user space).

Program Area, Parts Cx: The Defect Managed Area (DMA) consists of DMA segments, Cx. Each Cx consists of a spares area (SA) followed by a data area (DA). Each SA must contain 8 packets. Each DA within C1, C2, –, Cn-1, must contain 136 packets for primary data. Cn may contain less than 136 packets, based upon disc capacity. The DMA is the logical concatenation of all DAs.

Program Area, Part D STA: 33 packets reserved for secondary copies of the MTA structures.

Lead-out, Part A: Lead-out, no change

The number of Cx is determined as follows: P = number of 32 sector fixed packets available in the formatted track 1. The number of packets in all Cx is Pt = P . GAA size . STA size = P . 65. When Pt is divided by 144 (=8 + 136), there is a quotient Q and remainder R. If R .8, then Q = n, the DA size for each Cx is 136, and the lead-out begins R packets sooner. If R > 8, then Q = n . 1, the DA for C1, C2,...Cn-1 is 136, the DA for Cn is R . 8 packets in length, and the lead-out is not offset into the program area.

The Host's primary address space is the DMA. By default, an LBA is presumed to refer to this address space. Note that LBAs for the DMA do NOT match LBAs for a similarly formatted pre-MRW disc. The GAA is available for compatibility with older systems. The GAA LBA space is 0, 1, 2, 3, –, 1023d. Note that LBAs for the GAA exactly match LBAs for a similarly formatted pre-MRW disc.

Addressing

When method 2 addressing is used, the LBA of the first sector of the DMA is at the pre-MRW LBA of (32 + 8)*32 = 1280d. The following table shows the inequities with pre-MRW LBA references:

The GAA addressing is identical to traditional addressing. The new method of addressing sectors in the DMA is named "method 3 addressing" in the CD-MRW Defect Management & Physical Formatting. There is a small problem: there are two LBA spaces where formerly there was only one. The MRW Mode Page is used a the method of specific address space selection. The host may toggle between address spaces (DMA and GAA) by changing the logical units reference in the MRW Mode Page.

Host Requests/Logical unit Responses

The host may view the MRW disc as a removable magnetic medium with a 2048 byte sector size. This means that the random read capability of MMC is to be maintained and expanded to include the MRW disc. Additionally, random write capability must be added specifically for the MRW disc. Within the logical unit, only the writing of 32 sector fixed packets is allowed. MMC-1 and MMC-2 logical units share this restriction with their hosts. When MRW disc is present, the MRW compliant logical unit must not share this restriction with its host. This is a simple matter of implementing a read/modify/write for packets.

Background Formatting

Most of the process for formatting a CD-RW disc into the MRW format is performed in background. During this background formatting process, the disc is available for both read and write access within the LBA Space as it shall exist after formatting has completed. The MRW capable drive shall perform the necessary tasks to assure this access.

It is possible that the user may wish to remove the disc prior to format completion. This is allowed, however, the medium must be written in order to assure read compatibility with Multi-read capable read-only devices. This means that the disc must be closed. The format will begin again when a host arranges for the format to be restarted.

- How much free space i can have?

A CD-RW disc is mounted into a MRW capable CD-RW drive. The lead-in ATIP on this disc indicates that the first lead-in begins at 97:38:20 and the last possible lead-out begins at 75:04:12. Let us assume that the disc is completely formatted as a CD MRW disc.

The MRW format requires that the program area be formatted as a single track of fixed packets with 32 user sectors each. This gives us a maximum of 337812 sectors within the program area (from 00:00:00 to but not including 75:04:12). At 00:02:00 we will find the first user sector. This means that the first packet invades the track 1 pre-gap by 5 sectors. So, 337667 sectors may be dedicated to fixed packets. This yields 8658 packets with 5 sectors remaining (337 812 - (150 - 175) = 39 * 8 658 + 5). The 5 extra sectors are moved into the lead-out.

The GAA requires 32 packets from the beginning of the program area while the STA requires 33 packets at the end of the program area. This leaves 8 658 - 65 = 8593 packets for the DMA. Each SA/DA pair is 144 packets in length. 8593 = 59*144 + 97, so we may have 59 SA/DA pairs with 97 packets remaining. Of these 97 packets, 8 are reserved for the final SA, leaving 89 packets for the final DA. The actual number of user sectors in the DMA is 32*(59*136+89) = 25916.



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